Apparatus for cutting and excavating solids

ABSTRACT

An apparatus for cutting and breaking rock includes a cutting disc (13) having an attached wedge (11). Cutting disc (13) can be rotated by shaft (16) to cut a groove into rock. After a pre-determined distance, wedge (11) is forced into the cut groove to cause the rock above the groove to be broken away. Shaft (16) is powered by a drive motor, and can include a kick back mechanism to prevent wedge (11) from being trapped in the cut groove. The entire apparatus can be mounted to the three point linkage of a tractor.

TECHNICAL FIELD

THIS INVENTION relates to an apparatus for cutting and excavating solidsand particularly to an apparatus which can cut and break rock, coal,stone and the like.

BACKGROUND ART

Excavation of solids such as rock, coal, stone, ores, and the like isrequired in a variety of circumstances. These include in the miningindustry for recovering ore, quarries, recovery of coal, sinking of boreholes, excavation of tunnels and the like for sewerage, conduit lines,vehicles, and cutting of trenches, channels and the like.

It is known to excavate solids using basting techniques. However,blasting techniques are less suitable for excavation of tunnels,trenches or channels. Blasting also requires strict safety precautions.

Another technique to excavate solids is by using cutting or grindingapparatus. Such apparatus are provided with one or more cutting discswhich are provided with peripheral teeth (or picks). The discs areforced against the solid to be cut at extremely high forces and causethe solid to be cut away in small pieces.

A disadvantage with this type of apparatus is that the cutting processis extremely energy intensive and extremely energy inefficient. Thetechnique releases large amounts of heat and requires large equipment toprovide the necessary power to rotate the cutting discs and to force thecutting discs against a rock face.

Examples of such apparatus are found in the Wohlmeyer U.S. Pat. Nos.2,758,825, 3,297,101 and 3,379,024.

One disadvantage with excavating rock in a purely cutting process, isthe enormous wear and tear placed on the cutting disc and its cuttingteeth. Thus, a high degree of maintenance is required on the cutterdiscs.

The apparatus is also of a large size to accommodate the equipmentnecessary to power and hold the cutter discs. Thus, the apparatus isexpensive to use and maintain and is unsuitable for relativelysmall-scale excavations. These known apparatus are currently used intunnelling.

In order to improve the effectiveness of solid removal, it has beenknown to use a principle called "cut and break". In this process, anapparatus initially cuts a groove in the solid with a cutting disc andthen inserts a wedge into the cut groove in a separate action. The wedgecauses the rock or other solid to break away from the groove. Thus,excavation of the solid is due to a cutting action and a separatebreaking action.

A known apparatus using this cut and break technique is known as a"McKinlay Entry Driver" which appears to have been used in the U.S.A. inabout 1918.

The apparatus was limited in its use to cutting holes for tunnels andthe like and was unable to cut trenches.

This apparatus consisted of a horizontal shaft to which an arm wasmounted at right angles. The arm extended to each side of the shaft. Tothe arm were fixed a number of cutting plates which extended at rightangles to the arm. Upon rotation of the shaft, the arm was rotated andtherefore the cutting plates were rotated in a circular motion. When themachine was forced against a coal face, it caused annular grooves to becut into the coal face. On a secondary arm was fixed a wedge which wasexactly positioned such that upon rotation of the shaft, the wedge wascaused to enter into one of the grooves formed by the cutting platetherefore causing the coal to burst apart.

This type of apparatus still suffered from a number of disadvantagesincluding its size, complexity and expense.

Another disadvantage was the requirement to correctly position the wedgeon the secondary arm to ensure that it was caused to enter into a cutgroove and did not scrape against the coal face. If a particular cuttingplate was damaged and therefore resulted in a different type of groovebeing cut, this could result in the wedge not properly entering into thegroove. Furthermore, if a cutting plate was replaced, it was oftennecessary to ensure that the wedge was repositioned correctly.

Another disadvantage with the wedge (also called a "wedging wheel" or"bursting wheel") was the possibility of it becoming trapped in thegroove. Should this occur, and if the rock was extremely hard or did notburst, the result was that either the wedge would be destroyed ordeformed or that the motor driving the shaft would burn out.

Should the wedge be deformed or destroyed, it was necessary to shut downthe apparatus for replacement and re-positioning of the wedge.

Due to the difficulties with the wedges, the more modern cuttingmachines dispensed with them altogether.

DISCLOSURE OF THE INVENTION

We have now developed an apparatus which can utilise the cut and breakprinciple of excavation and where the difficulties in using the wedge asdescribed above may have been substantially overcome.

We achieve this by positioning the wedge on the cutting disc. Thus,there is no requirement for secondary arms and there is no requirementto ensure that the wedge is accurately positioned on a secondary arm.

As an option, we can provide an apparatus with a "kick-back" mechanismto minimise the possibility of the wedge being trapped in the cutgroove.

Therefore, in one form the invention resides in an apparatus for cuttingand breaking a solid, the apparatus having a cutting disc with aperipheral edge, a top wall and a bottom wall, and a wedge located on atleast one of said walls and extending therefrom and spaced inwardlyrelative to the peripheral edge of the cutting disc.

In this manner, we find that the cutting disc can initially cut thegroove and when the groove is at a predetermined depth (corresponding tothe spacing between the periphery of the cutting disc and the wedge),the wedge will enter into the cut groove and will cause the solid to bebroken.

The wedge may be provided on either the top wall or the bottom wall andit is preferred that a wedge is provided on both the top wall and thebottom wall of the cutting disc.

If desired, the wedge may be rotatably mounted relative to the cuttingdisc. In this manner, the wedge may be rotatably inserted into a cutgroove which may minimise wear.

Suitably, a pair of wedges are provided, one on the top wall and one onthe bottom wall of the cutting disc and whereby the wedges can beconnected together.

The wedge may be adjustably mounted to the cutter disc to allow it toextend from the cutter disc at a plurality of distances. This may be ofadvantage should the hardness of the vary according to cutting depth. Itmay also allow the cutting disc to enter deeply into the cut groove withsubsequent expansion of the wedge to cause the rock to break.

The wedge may be spaced inwardly from the peripheral edge of the cuttingdisc by varying distances depending on the type of rock to be cut andthe cutting action, power capability of the apparatus and the like. Forinstance, with soft friable solid, the wedge can be spaced more towardsthe peripheral edge and can have a higher raised profile. For hardfriable rock, the wedge can be spaced closer to the centre of thecutting disc to improve its leverage. For hard non-friable rock, thewedge height may be reduced.

The profile of the wedge surface may vary and may depend on the type ofsolid to be cut and the type of cutting action.

If the wedge is rotatably mounted to the cutting disc, it is preferredthat the wedge profile is symmetrical about its rotation axis. One typeof profile may include a cone shape or a "pyramid" shape (also called a"mushroom" shape). The angle of the profile (i.e., the distance that thewedge can be raised above the cutting disc) may also vary. The angle maybe between 1° to 10°, if desired. If a pair of wedges are provided, eachwedge may have an identical or a different profile relative to theother. In one form, the wedges may have identical profiles while inanother form, one wedge may be substantially planar while the otherwedge may have pyramid type shape.

It is preferred that the apparatus is provided with a pair of wedgeswhich are connected to an attachment member, the attachment member beingmountable in an aperture in the cutting disc. The attachment member maythreadingly engage with the opening in the cutting disc.

The cutting disc may be substantially circular when viewed in plan. Theperiphery of the disc may be slightly thickened relative to theremaining body of the disc. One or more cutting teeth may be providedand these may be mounted adjacent the periphery of the cutting disc.Preferably, a plurality of cutting teeth are provided. The teeth may beequally spaced about the periphery of the disc but it is preferred thatcutting teeth are not present in the immediate vicinity of the wedge.The cutting teeth may be at various angles and it is preferred that someof the cutting teeth extend upwardly from the cutting disc, some of thecutting teeth are in line with the cutting disc and some of the cuttingteeth are spaced downwardly from the cutting disc. This can ensure thatthe cut groove is sufficiently large to accommodate the cutting discwithout the cutting disc itself becoming wedged in the groove.

The cutting disc may be attachable to adjacent one end of a rotatableshaft member. The rotatable shaft member may be driven by a drive means.The drive means may be hydraulic, pneumatic, electric or internalcombustion.

Suitably, the drive means is coupled to a reduction gearbox to providethe rotatable shaft member with a lower rotating speed but high torque.

The shaft may be supported by support framework. The support frameworkmay also support the drive means and gearbox.

The rotatable shaft member may be biasable towards and away from thesolid to be cut, by a biasing means. Preferably, the biasing means issufficient to provide sufficient force to the cutting disc to allow itto efficiently cut into the solid, however, not strong enough to prevent"kick-back" of the rotatable shaft member should the wedge become Jammedor stuck within the cut groove.

The biasing means may be hydraulic, pneumatic or mechanical. Suitably,the supporting framework is pivotly mounted and the biasing means canfunction to bias the supporting framework and therefore the rotatableshaft member towards and away from the solid to be cut.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will now be described with reference tothe drawings in which

FIG. 1 illustrates a cutting disc according to an embodiment of theinvention, including a wedge;

FIG. 2 illustrates the positioning of a pair of wedges on the cuttingdisc of FIG. 1;

FIG. 3 is a side part section view of the cutting disc of FIG. 1 in use;

FIG. 4 is a view of an apparatus to rotate the cutting disc asillustrated in FIG. 1;

FIG. 5 is a view of the apparatus of FIG. 4 attached to the three-pointlinkage of a tractor;

FIG. 6 illustrates in greater detail the linkage of FIG. 5;

FIG. 7 illustrates the cutting disc being used;

FIG. 8 illustrates a cutting disc having an alternative wedgearrangement;

FIG. 9 illustrates a cutting disc having yet a further alternative wedgearrangement.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Referring to FIG. 1 there is illustrated a cutting disc 10 to which isfitted a wedge 11. Cutting disc 10 is more or less of conventionaldesign and is circular when viewed in plan. Cutting disc 10 is providedwith a top wall 13 and a bottom wall 14. Top wall 13 is slightly smallerin diameter relative to bottom wall 14, thereby resulting in peripheraledge 12 being outwardly tapered. Peripheral edge 12 is also thickenedrelative to the main portion of top wall 13 as is illustrated in FIG. 1.

Attached to peripheral edge 12 are a plurality of cutting teeth or picks15. Picks 15 are conventional insert picks, in which a tungsten carbidetool tip is inserted into an axial hole in the steel main body of thepick and are used for gauge cutting. Capped picks in which the tungstencarbide tool tip takes the form of a blunt pointed cap covering the endof a steel shank of the pick are used for the rest of the cutting. Thepicks are conventionally laced apart from having two pairs of cuttersfor gauge cutting. The reason for using two pairs of gauge cutters is toensure that the groove which is cut has sharp stress-concentratingcorners, making for easy breaking. Picks 15 are arranged such that someof the picks extend above top wall 13, some of the picks extend belowbottom wall 14 and some of the picks are in line. It is also noted thatpicks 15 are absent at the periphery immediately around wedge 11.Cutting disc 10 is mounted to a rotatable shaft 16 which itself can berotated by a drive means which shall be described in greater detailbelow and with reference to FIG. 4.

Wedge assembly 11 is formed from a pair of wedges being upper wedge 17and lower wedge 18, more clearly shown with reference to FIGS. 2 and 3.Each of wedges 17 and 18 in this embodiment have a "pyramid" or"mushroom" profile. Each of wedges 17 and 18 include a depending collarportion 19, 20 with collar portion 20 being of reduced diameter relativeto collar portion 19 to enable one to slide within the other. Collarportion 20 includes an annular groove 21 in which can be fitted a clip22 to fit wedges 17 and 18 together. In this arrangement, wedges 17 and18 are free to rotate relative to each other. Wedges 17 and 18 arefitted to an attachment portion 23 which is in the form of a annulushaving an external thread. The annulus fits within a correspondingthreaded opening within cutting disc 10 and this results in attachmentportion 23 being securely threadingly engaged with cutting disc 13.Collar portions 19 and 20 can fit within attachment portion 23. There isabout a 1 mm clearance between the various parts to allow dirt which mayenter the arrangement to leave but without allowing larger particles toget in. The parts are easily assembled but requires a sledgehammer andwedges to take them apart.

FIG. 3 shows a part section view of the cutting disc 13 and wedgeassembly 11 of FIG. 1 and shows how the various parts can be fittedtogether.

Cutting disc 10 is rotated and mounted by an assembly, an embodiment ofwhich is illustrated in FIG. 4.

The assembly comprises cutting disc 10 fitted to rotating shaft 16.Rotating shaft 16 is supported through a bearing in supporting framework24 (bearing not shown).

Upper end of shaft 16 is connected to a reduction gearbox 25. Theassembly can be fitted to a three-point linkage of a tractor and can bepowered from the output drive shaft or power take-off (not shown) of thetractor. The output drive shaft of the tractor typically rotates at anominal 1,000 rpm and can be rated at approximately 20 kW. The outputdrive shaft of the tractor drives a fixed capacity hydraulic pump 26having a displacement of about 50 ml per revolution. The hydraulic oilat a maximum nominal 3,000 psi pressure drives a variable capacity motor27 having a maximum displacement of 105 ml, minimum of about a quarterof that figure.

The variable capacity provides the possibility of varying the speed ofthe final drive.

Motor 27 drives gearbox 25 which is a 25:1 reduction gearbox ofsubstantial dimensions to bring the final speed down to a nominal 20rpm. The system is designed for average torque of 5,000 Nm. The gearboxis of a variety whereby the shaft passes through the gearbox, the onlyconnection between the gearbox and the frame of the machine, apart fromthe shaft being by a torque arm 28. The gearbox is manufactured byBonfiglioni.

Supporting framework 24 is pivotly mounted to a second support 29, withsecond support 29 being pivotly mounted to link arms 30 which form partof the tractor linkage assembly. The pivot mounting point is illustratedas 30A.

Framework 24 is fitted at an upper portion thereof to a biasing means inthe form of an hydraulic ram 31 which is itself powered by the tractor.Hydraulic ram 31 also functions to allow cutting disc 10 to "kick-back"should wedge assembly 11 become trapped within the cut groove and asshall be described in greater detail below.

Counter-weights 32 are provided to balance the assembly.

The angle by which shaft 16 (and therefore cutting disc 10) extendsbelow the drive assembly can be varied through attachment points 33. Itcan be seen that three attachment points are provided and by inserting afastener into a particular attachment point, frame assembly 24 can bemoved to different angle configurations which will in turn will vary theangle of shaft 16 and therefore cutting disc 10. The angle can vary tothe vertical of 5° to 25°.

FIG. 5 illustrates the apparatus attached to a tractor and like numbershave been used to illustrate like components. The apparatus can befitted to the three-point linkage arms of the tractor, together with aparallelogram linkage for the main frame, detail of which is shown withrespect to FIG. 6.

As the tractor illustrated in FIG. 1 (or other like vehicle) is providedwith pneumatic wheels 40, a pair of stabilisers 41 are provided toprevent rocking of the apparatus during use. The stabilisers are in theform of steel rollers which can be fitted to second support 29 throughbox 42 (see FIG. 4). The arrangement also allows the rollers to beadjustable in length. Hydraulic rams may be used to push rollers 41 ontothe ground to transfer some of the weight of the tractor from thetractor tyres to the rollers 40.

Hydraulic ram 31 (see FIG. 4) is fitted to allow the top link of theparallelogram linkage arrangement to shorten slightly when it is underlarge compressive load. This allows cutting disc 10 to move backwardsslightly. Hydraulic ram 31 is filled with oil under pressure of gas in areservoir. When the load on ram 31 exceeds the force exerted on the ramby the pressurised oil, the ram is forced back allowing the upper linkto shorten. The process is one which increases the pressure of the gasin a reservoir, and so force required to shorten the link becomesprogressively larger. The rate of increase is governed by the gas volumein the reservoir, the pressure and volume in turn being determined bythe initial pressure of the gas in the reservoir and the volume of oilsubsequently admitted.

In use, to cut into a flat surface, cutting disc 10 is lowered into acontact position (the angle being determined through pivot 33) andpressure is then applied to cutting disc 10 to excavate a shallow cut.The tractor is advanced very slightly and the cut is deepened andwidened slightly. By creeping very slowly forward as disc 10 cuts, it ispossible to bury the disc until rollers 41 bear on the ground surfaceand the cutting wheel is ready to operate at the desired depth.

The present machine is driven forward by a winch, which runs slowlybecause of a small choke orifice being placed in the oil supply line toit. The effect of the choke is to ensure that the winch has almost zerotorque when it is running at its maximum speed, the torque becominggreater as the winch slows, reaching a maximum just as it is about tostall. The forward speed of the tractor is so slow that in practice thewinch is running at a speed not much above a stall. In this condition,the advance of the tractor depends upon the progress of the cuttingwheel, and this cuts faster the greater the load upon it, up until thepoint is reached when the cutting wheel drive stalls because the drivemotor can no longer provide the necessary force to rotate it. Moderatelysensitive control of the near-stall force from the winch is obtainedthrough the use of a pressure regulating valve in the winch hydraulicline, which sets a maximum pressure which may be applied to the winch.In practice the driver watches the pressure gauge in the oil supply lineto the cutting wheel motor, and adjusts the pressure of the oil in thewinch drive so as to keep the cutting wheel drive pressure close to themaximum of which the drive system is capable of supplying. Should thecutting wheel stall, the pressure to the winch is reduced, and this isusually sufficient to allow the cutting wheel to restart. This isobviously unsatisfactory for any but an experimental machine, andproposed future machines will incorporate an automatic system to controlthe advance of the machine whilst ensuring the cutting wheel picks arealways operating at a load close to the maximum.

Referring to FIGS. 7 to 9, there are shown various wedge assemblies. InFIG. 7, top wedge 50 and bottom wedge 51 have the same profile. Theangle of bottom wedge 51 in the embodiment is chosen to be the same asthe angle of inclination of cutting disc 10 so that bottom wedge 51 liesflat upon the excavated bottom of the cut groove. The shape of the topwedge 50 can depend upon the type of rock being excavated and inparticular upon the rock strength and its friability. Friable rock(i.e., sandstone) wears away quickly and so the top of wedge 50 needs tobe higher to compensate for this than is the case with a wear-resistantrock.

FIG. 8 shows an alternative wedge arrangement wherein top wedge 52 issubstantially planar and bottom wedge 53 is of a pyramid shape.

Referring to FIG. 9, in this embodiment the wedge assembly isparticularly suitable for hard, strong and wear-resistant rock. Thewedge assembly in this arrangement comprises a top wedge 55 where thetrailing surface 56 is caused to wedge within the cut to form thebursting action rather than leading surface 57. In this arrangement,much more leverage is applied than is the case with reference to FIGS. 7and 8.

Various changes and modifications may be made to the embodimentdescribed. For instance, cutting disc 10 may contain a number of wedges11 and may contain a number of sets of wedges. We believe that largecutting discs can be fitted with two or more of the wedge assemblies.The wedges may rotate relative to cutting disc 10 or may be fixedthereto, or if they do rotate, may rotate independently of other wedges.

The wedges may be expandable or retractable such that it extends abovethe general profile of the cutting disc to break the under-cut material.It is envisaged that this could be achieved by including a hydraulic ramor by admitting high-pressure water through cutting disc 10 to operatethe wedges. If high-pressure water is used, it may also be passedthrough nozzles to have the dual effect of flushing away debris andexerting an extra large force on the under-cut material.

Thus, rotating shaft 16 may be hollow and a space may be provided with aphasing valve to be used with a high-pressure water supply. This mayincrease the efficiency of the picks.

It may be possible to enclose shaft 16 within a strong sleeve which maybe fitted with a wedged shape, pointed leading edge so that should theunder-cut rock reach the shaft without breaking, there may be asplitting action to break the under-cut rock. This may be advantageouswhen cutting rock with a tendency to split into large flat slabs as dosome sedimentary rocks, so that the bursting wheel has broken free alarge slab which just lies in position, preventing forward motion of themachine. Alternatively, shaft 16 may be fitted with picks or other formsof cutting teeth so it may cut its own path.

A number of cutting discs may be provided. If only one cutting disc isprovided, there is a tendency for the apparatus to "walk" sideways asthe torque from the cutting process generates a sideways force ofseveral tonnes. This may be resisted by tying the tractor (or othervehicle) by chains or like members. Therefore, one further alternativemay include providing a pair of cutting wheels which may rotate in acontra rotating manner such that the sideways force of one is cancelledby the other.

Multiple cutting discs may be arranged in a single line perpendicular tothe motion of the machine. Thus, a first cutting disc may cut an initialtrench and a second one may deepen it.

The cutting wheel can be trust into the rock with a force of about 8,000lb or 4 tonnes. This implies a cutting force of about 2.5 tonnes whichin turn requires a torque of about 5,000 Nm if the cutting disc is about400 mm in diameter. Larger cutting discs will require larger forces andlarger torques. By making the cutting disc free of picks in the vicinityof the wedge, all the thrust and torque is available to push the wedgeinto the groove to break the under-cut material away.

It should be appreciated that various other changes and modificationsmay be made to the embodiment described without departing from thespirit and scope of the invention.

I claim:
 1. An apparatus for cutting and breaking a solid, the apparatushaving a cutting disc with a peripheral edge, a top wall and a bottomwall, a first wedge extending from the top wall, and a second wedgeextending from the bottom wall, said first and second wedges beingspaced inwardly relative to the peripheral edge of the cutting disc, theperipheral edge being provided with a plurality of cutting picks.
 2. Theapparatus as claimed in claim 1, wherein the first and second wedges areconnected together.
 3. The apparatus as claimed in claim 2, wherein thefirst and second wedges are releasably mounted relative to each other,and to the cutting disc.
 4. The apparatus of claim 3, wherein at leastone of said first and second wedges has an inclined leading face.
 5. Theapparatus as claimed in claim 4, wherein the inclined angle is between 1to 10 degrees.
 6. The apparatus as claimed in claim 1, furthercomprising a rotatable shaft member connected to the cutting disc, theshaft member being rotatably driven by a drive.
 7. The apparatus ofclaim 6, including means for biasing the rotatable shaft member and thecutting disc against the solid to be cut.
 8. The apparatus as claimed inclaim 7, wherein said means for biasing provides sufficient force to thecutting disc to allow it to cut into the solid, but allows the shaftmember to kick back should the wedge become jammed or stuck within thesolid.
 9. The apparatus as claimed in claim 8, wherein said drive andbiassing means is supported by frame assembly which is attachable to avehicle.
 10. The apparatus as claimed in claim 9, in combination withthe vehicle, and including ground engageable stabilisers to restrictsideways movement of the vehicle upon use of the apparatus.
 11. Anapparatus for cutting and breaking a solid, the apparatus comprising amember having a centre of rotation and adapted to be mounted forrotation to a shaft, the member having a generally planar main bodyportion and a peripheral edge, the peripheral edge having a cutting edgeadapted to accommodate a plurality of cutting picks, a top of theperipheral edge being raised above the main body portion extendingimmediately behind the peripheral edge, and at least one wedge locatedon the main body portion and spaced inwardly relative to the peripheraledge.
 12. The apparatus of claim 11 wherein said at least one wedge ismounted for rotation relative to the main body portion.
 13. Theapparatus of claim 12, wherein said at least one wedge comprises a firstwedge extending from a top wall of the main body portion and a secondwedge extending from a bottom wall of the main body portion.
 14. Theapparatus of claim 12, wherein said at least one wedge is movablebetween an extended and retracted position relative to the main bodymember.
 15. The apparatus of claim 11, wherein said at least one wedgeis movable between an extended and a retracted position relative to themain body member.
 16. An apparatus for cutting and breaking a solid, theapparatus comprising a member having a centre of rotation and adapted tobe mounted for rotation to a shaft, the member having a generally planarmain body portion and a peripheral edge, the peripheral edge having acutting edge adapted to accommodate a plurality of cutting picks, theapparatus further having a first wedge extending from a top wall of themain body portion, and a second wedge extending from a bottom wall ofthe main body portion, the wedges being mounted for rotation relative tothe main body portion.
 17. The apparatus of claim 16, wherein said atleast said first wedge is movable between an extended and retractedposition relative to the main body member.
 18. An apparatus for cuttingand breaking a solid, the apparatus comprising a member having a centreof rotation and adapted to be mounted for rotation to a shaft, themember having a generally planar main body portion and a peripheraledge, the peripheral edge having a cutting edge adapted to accommodate aplurality of cutting picks, the apparatus further having a wedge locatedon the main body portion, the wedge being movable between an expandedand a retracted position relative to the main body portion.